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Modélisation cinétique du vieillissement radio-thermique du polyéthylène réticulé silane chargé d’ATH destiné à l'isolation de câbles électriques dans les centrales nucléaires.

Abstract : Cross-linked low density polyethylene (XLPE) is widely used in the insulation of power cables in nuclear power plants. Electrical cables are exposed to ionising radiation and relatively high temperatures which leads to the degradation of the insulating polymer. Therefore, the objective of this thesis was to elucidate the radio-thermal ageing of the pure and aluminium trihydrate (ATH) filled XLPE and to develop a kinetic model to predict the lifetime of these insulations. A multi-scale approach was used to evaluate the impact of radio-thermal ageing on the molecular, macromolecular and morphological structures and on the usage properties of the polymer. This study showed that chain scissions lead to an increase in the crystallinity ratio and the thickening of the crystalline lamellae, thus leading to the confinement of the amorphous phase and consequently to the embrittlement of the material. As a result of this study an analytical model was developed which was then completed by several structure/property relationships in order to also predict the changes in the dielectric properties. The impact of ATH fillers on the radiothermal ageing of the Si-XLPE matrix was then studied. This study showed that the fillers had no influence on the oxidation and crystallisation kinetics, and consequently on the densification kinetics of the Si-XLPE matrix. It was found that the changes in the elastic properties are mainly induced by the crystallinity of the Si-XLPE matrix. In contrast, the changes in fracture properties are significantly impacted by the degradation of the ATH/Si-XLPE interface. Finally, the kinetic model previously developed for the pure Si-XLPE matrix was extended to composite materials by taking into account both the dilution effect of ATH fillers and the interfacial degradation.
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Submitted on : Friday, July 29, 2022 - 3:48:11 PM
Last modification on : Friday, August 5, 2022 - 3:33:42 PM

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  • HAL Id : tel-03740554, version 1

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Sarah Hettal. Modélisation cinétique du vieillissement radio-thermique du polyéthylène réticulé silane chargé d’ATH destiné à l'isolation de câbles électriques dans les centrales nucléaires.. Mécanique des matériaux [physics.class-ph]. HESAM Université, 2022. Français. ⟨NNT : 2022HESAE034⟩. ⟨tel-03740554⟩

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